1. Field of the Invention
The present invention relates to an image restoration apparatus that obtains information on the degradation caused in an image shot by a digital camera or the like, that is, a degradation function, and estimates the pre-degradation image (restored image) from the degraded shot image by the iteration method.
2. Description of the Related Art
Various techniques to restore the degradation of an image shot by a digital camera or the like have been proposed.
As such an image restoration method, one based on the iteration method using iterative calculations is known. According to this restoration method, image modification and update and image degradation by use of a degradation function are iterated, and the degraded image is compared with the shot image. When the residual obtained by the comparison is smaller than a predetermined threshold value, the corresponding updated image is estimated to be the restored image. The principle of this image restoration is described, for example, in a document “M. Elad and A. Feuer; Super-Resolution of an Image Sequence-Adaptive Filtering Approach; Technion-Israel Institute of Technology, Apr. 4, 1997.”
However, when a shot image degraded by an asymmetric degrading filter is restored by use of iterative calculations as described in the above-mentioned document, the image restoration accuracy is low. In addition, many iterative calculations are required, so that the restoration requires much time.
The present invention is made in view of such a technical background, and an object thereof is to provide an image restoration apparatus capable of restoring a shot image degraded by an asymmetric degrading filter, in a short time with a high degree of accuracy.